ICD-10-CM Diagnosis Code M65.90 - Unspecified synovitis and tenosynovitis, unspecified site (original) (raw)

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ICD List 2025-2026 Edition

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Unspecified synovitis and tenosynovitis, unspecified site

ICD-10-CM Code:

M65.90

ICD-10 Code for:

Unspecified synovitis and tenosynovitis, unspecified site

Is Billable?

Yes - Valid for Submission

Chronic Condition Indicator: [1]

Not chronic

Code Navigator:

M65.90 is a billable diagnosis code used to specify a medical diagnosis of unspecified synovitis and tenosynovitis, unspecified site. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026.

Unspecified diagnosis codes like M65.90 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

  1. Code Information
  2. Approximate Synonyms
  3. Clinical Classification
  4. Clinical Information
  5. Tabular List of Diseases and Injuries
  6. Index to Diseases and Injuries References
  8. Diagnostic Related Groups Mapping
  9. Replacement Code
  10. Patient Education
  11. Other Codes Used Similar Conditions
  12. Code History

The following list of clinical terms are approximate synonyms, alternative descriptions, or common phrases that might be used by patients, healthcare providers, or medical coders to describe the same condition. These synonyms and related diagnosis terms are often used when searching for an ICD-10 code, especially when the exact medical terminology is unclear. Whether you're looking for lay terms, similar diagnosis names, or common language alternatives, this list can help guide you to the correct ICD-10 classification.

Clinical Classifications group individual ICD-10-CM diagnosis codes into broader, clinically meaningful categories. These categories help simplify complex data by organizing related conditions under common clinical themes.

They are especially useful for data analysis, reporting, and clinical decision-making. Even when diagnosis codes differ, similar conditions can be grouped together based on their clinical relevance. Each category is assigned a unique CCSR code that represents a specific clinical concept, often tied to a body system or medical specialty.

CCSR Code: MUS009

Inpatient Default: Y - Yes, default inpatient assignment for principal diagnosis or first-listed diagnosis.

Outpatient Default: Y - Yes, default outpatient assignment for principal diagnosis or first-listed diagnosis.

syndrome consisting of synovitis; acne conglobata; palmoplantar pustulosis; hyperostosis; and osteitis. the most common site of the disease is the upper anterior chest wall, characterized by predominantly osteosclerotic lesions, hyperostosis, and arthritis of the adjacent joints. the association of sterile inflammatory bone lesions and neutrophilic skin eruptions is indicative of this syndrome.

inflammation of the synovial membrane.

diffuse outgrowth arising from the synovial membrane; synovial bursa; or tendon sheath around the joint cavity, with extension to surrounding soft tissue. it is characterized by pigmented hemosiderin-containing macrophages; foam cells; and multinucleated giant cells. it usually occurs in the hands and feet, and around large joints, such as in the ankle and knee joints.

a tumor arising in the synovial membrane; synovial bursa; or tendon sheath. it is characterized by osteoclast-like giant cells; foam cells; pigmented hemosiderin-laden macrophages and inflammatory infiltrate. it is classified either as diffuse or localized tenosynovitis.

narrowing or stenosis of a tendon's retinacular sheath. it occurs most often in the hand or wrist but can also be found in the foot or ankle. the most common types are de quervain disease and trigger finger disorder.

inflammation of the synovial lining of a tendon sheath. causes include trauma, tendon stress, bacterial disease (gonorrhea, tuberculosis), rheumatic disease, and gout. common sites are the hand, wrist, shoulder capsule, hip capsule, hamstring muscles, and achilles tendon. the tendon sheaths become inflamed and painful, and accumulate fluid. joint mobility is usually reduced.

the inner membrane of a joint capsule surrounding a freely movable joint. it is loosely attached to the external fibrous capsule and secretes synovial fluid.

inflammation at the site of insertion of ligaments, tendons, and other fibrous structures into bone.

a category of juvenile idiopathic arthritis associated with arthritis and enthesitis, which may involve the axial skeleton. it is a form of juvenile spondyloarthritis.

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

References found for this diagnosis code in the External Cause of Injuries Index:

M6590 replaces the following previously assigned ICD-10-CM code(s):